Exploring what the recent Noakes review misses
A recent review by Noakes and colleagues, Carbohydrate Ingestion on Exercise Metabolism and Physical Performance, has been making waves in endurance sport. If you follow triathlon science or coaching discussions on social media, you have likely seen it referenced already. The paper challenges long-held assumptions about carbohydrate intake, fatigue, and endurance performance, claiming that remarkably little carbohydrate is needed to achieve optimal performance.
At its core, the review argues that athletes slow primarily due to declining blood glucose rather than muscle glycogen depletion. From that perspective, relatively modest carbohydrate intake (as little as 10 g/h, as the review posits) may be sufficient to prevent hypoglycemia and support prolonged exercise. That conclusion has caught attention because it runs counter to how many high-level athletes currently fuel in training and racing.
In this article, I want to break down the review, examine where it is strong, and look closely at where its conclusions begin to fray when applied to high-performance endurance racing and training. My goal is not to dismiss the paper, but to place it in proper context and to explore what the review does not fully explain about performance, durability, and recovery.
Reactions to the paper have been predictably polarized. Some see it as support for minimalist, lower-carbohydrate fueling approaches. Others dismiss it outright as disconnected from modern racing. Endurance nutrition has become strangely moralized, with athletes identifying as “high-carb” or “low-carb” as if these labels reflect allegiance rather than strategy. Both perspectives miss the point.
As with any scientific review, it is important to remember that this paper synthesizes existing studies rather than presenting new experimental data. It is extensive and thoughtfully written, and it does an excellent job dismantling the simplistic fuel-tank model of glycogen depletion that still lingers in endurance culture. Where the paper becomes less satisfying is in what replaces that model. Framing carbohydrate primarily as a tool to prevent falling blood glucose levels underplays what else is happening during prolonged, high-intensity endurance exercise and how higher carbohydrate availability can positively influence performance and recovery.
What I aim to do in this article
To be clear and upfront, here is what I aim to do in this article.
First, acknowledge where the review is clearly right. Second, explain where the conclusions become incomplete when applied to real racing and recovery. Third, connect the physiology to what we consistently observe in high-performing endurance athletes and their steady move toward carbohydrate intakes in the range of 60 to 120 grams per hour during competition.
As a coach working with high-level triathletes, I see what happens at the sharp end of the sport. The pattern is remarkably consistent. Athletes are reaching new levels of performance by increasing carbohydrate intake during training and racing. These are athletes who experiment carefully, who have access to strong scientific support, and who are relentlessly focused on what actually improves performance. Through that process, higher carbohydrate intake (within reason) has repeatedly been associated with better pacing, lower perceived exertion, and improved recovery.
Pointing to what elite athletes do is not, by itself, proof of anything scientific. The science still matters. But it is useful to examine this question of carbohydrate intake through the lens of high-performance training and racing. We know it is possible to finish an Ironman on very little carbohydrate. The more important question is whether minimal carbohydrate intake supports maximal performance in athletes racing at high intensities and pushing the limits of their physiology.
If you want to understand why the best athletes fuel the way they do, and why the available scientific evidence suggests that very low carbohydrate intake is unlikely to support peak performance in long-course racing, keep reading.
What the Review Gets Right
The review's most valuable contribution is dismantling the outdated "fuel tank" model of fatigue.
Muscle ATP doesn't fall to critically low levels at exhaustion. If glycogen depletion directly caused fatigue through energy crisis, we would expect catastrophic muscular failure, like an engine seizing without oil. Instead, we see a controlled, regulated reduction in pacing. Athletes slow long before their muscles are incapable of generating force.
This matters and supports that the classic model, that you burn through glycogen until you hit a metabolic wall (the dreaded bonk!), doesn't match what the science shows.
The alternative view, that the brain regulates exercise intensity to prevent physiological catastrophe, better explains what fatigue actually looks like. Fatigue is regulated rather than absolute, and the review is particularly strong on explaining the link between blood glucose and performance. The authors clearly demonstrate that exercise-induced hypoglycemia correlates with exercise termination. When blood glucose drops below starting values during prolonged exercise, performance deteriorates, even when muscle glycogen remains available.
Carbohydrate ingestion prevents or reverses this decline. The liver's role in maintaining glucose availability becomes increasingly strained during prolonged exercise, and carbohydrate intake protects that system. This reframes fueling usefully. In long endurance events, fuel strategies must protect central drive and neural function rather than simply topping up muscle glycogen. The review demonstrates this well.
The review also rightly criticizes blanket recommendations for high carbohydrate intake across all training contexts. Many recreational athletes train at intensities where fat oxidation provides most of the energy. Aggressive carbohydrate fueling during easy sessions or short workouts is unnecessary and counterproductive. For easy aerobic work, short efforts, and sessions well below threshold, 90-120 g/h makes no sense. Fueling should match training stimulus and metabolic demand.
Where the Review Falls Short and Why It Matters
Here is where I will be direct. The review's central conclusion, that 10 g/h of carbohydrate (or 15-30 g/h, depending on the section) is sufficient for optimal performance because higher intakes don't produce dose-dependent improvements, fundamentally misrepresents both the research evidence and competitive reality as it relates to performance and recovery.
The review argues that because the "lowest dose tested usually produces ergogenic effects equivalent to those produced by much higher rates of CHO ingestion," there's no benefit to consuming more than minimal amounts during exercise. This cherry-picks findings and ignores substantial controlled research showing clear benefits of higher carbohydrate intake.
Controlled performance trials consistently show benefits beyond hypoglycemia prevention. King et al. found that consumption of 90 grams of carbohydrates per hour led to superior performance during a 30-min TT after 2 hours of riding at 77% of VO2 max compared to taking in 60g or 75g (notably, 112.5g was not better than 90g. You need to test what works best for you).
A controlled laboratory study by Smith and colleagues tested whether higher carbohydrate intake during prolonged cycling improves performance in a dose-dependent manner. Trained cyclists completed two hours at approximately 77 percent of VO₂max followed by a 20-kilometer time trial while ingesting 15, 30, or 60 grams of carbohydrate per hour. Time-trial performance improved progressively with higher carbohydrate intake, with the greatest mean power output observed in the 60 g/h condition. These improvements tracked with higher rates of exogenous carbohydrate oxidation and occurred without meaningful muscle glycogen sparing, supporting the idea that greater carbohydrate availability can enhance endurance performance by increasing sustainable energy flux rather than simply preventing hypoglycemia.
Currell and Jeukendrup compared carbohydrate ingestion during prolonged cycling using a glucose-only solution and a glucose–fructose mixture, both provided at the same total ingestion rate of approximately 1.8 g per minute. Despite identical carbohydrate intake rates, athletes consuming the glucose–fructose mixture demonstrated an approximately 8% improvement in time-trial performance compared with the glucose-only condition. In this way, the key distinction was not total carbohydrate intake, but delivery and oxidation. The glucose–fructose mixture increased intestinal absorption and exogenous carbohydrate oxidation by engaging multiple transport pathways. If carbohydrate’s sole role were simply to prevent a decline in blood glucose, differences in absorption rate and oxidation capacity would not be expected to translate into meaningful performance gains. Instead, these findings support the idea that higher carbohydrate availability and oxidation can directly enhance performance by supporting greater metabolic throughput during sustained high-intensity exercise.
Applied field studies also show positive dose-response effects. The 2020 study by Viribay and colleagues is revealing. Elite mountain marathon runners were randomized to 60, 90, or 120 g/h of carbohydrate during competition. Athletes in the 120 g/h group exhibited significantly lower markers of exercise-induced muscle damage, including creatine kinase and lactate dehydrogenase, as well as a lower internal exercise load based on perceived exertion. Importantly, these differences occurred despite similar external workloads, indicating reduced systemic stress rather than simple differences in pacing.The companion study by Urdampilleta found that runners who consumed 120 g/h of carbohydrate experienced smaller declines in jump performance and strength tests from before the race to 24 hours after, and preserved greater high-intensity run capacity in the post-race testing compared with those consuming lower carbohydrate rates. Together, these findings show that very high carbohydrate intake in prolonged, high-stress endurance events is associated with reduced physiological strain and better post-event neuromuscular preservation and recovery, outcomes that are closely linked to racing performance, durability, and recovery from big training/racing days, even if the study designs do not directly measure finish times.
Taken together, this body of evidence makes it difficult to defend the idea that minimal carbohydrate intake is sufficient for optimal endurance performance. While small amounts of carbohydrate can prevent overt hypoglycemia, controlled laboratory trials and applied field studies consistently show that higher carbohydrate availability improves performance capacity, reduces physiological strain, and supports recovery in ways that go well beyond blood glucose maintenance alone. These benefits appear most clearly when exercise intensity is high, duration is long, and athletes are asked to perform again, either later in the effort or in subsequent training.
The Mechanism: Why ATP Flux Matters
To understand why higher carbohydrate intake improves performance beyond simply preventing hypoglycemia, it helps to focus on how fuel is actually used at the cellular level.
ATP is generated through multiple pathways, not just inside the mitochondria. Glycolysis occurs in the cytosol and produces ATP immediately, without requiring oxygen. That ATP is small in absolute quantity, but critically important when energy demand rises quickly or fluctuates. At the same time, glycolysis produces pyruvate, which can be transported into the mitochondria and oxidized (just like with fatty acids) to generate much larger amounts of ATP through the Krebs cycle and oxidative phosphorylation.
What differs is the rate at which ATP can be generated.
Fat oxidation draws from a virtually unlimited energy reserve, but ATP delivery is relatively slow and constrained by oxygen availability and transport. This makes fat an excellent fuel for steady, moderate-intensity work where energy demand is predictable, and pace changes are minimal.
Carbohydrate metabolism during hard training provides two advantages that fat cannot. First, glycolysis supplies immediate ATP in the cytosol, supporting rapid changes in force production and pace. Second, carbohydrate oxidation via pyruvate supports faster mitochondrial ATP production at a lower oxygen cost per unit of ATP. Together, these properties allow athletes to sustain higher outputs and respond more effectively to surges, terrain changes, and late-race demands.
This matters because long-course triathlon is not raced at static, low-intensity outputs. Even in a 70.3 or Ironman, athletes spend substantial portions of the race at intensities that require high ATP flux, with repeated surges layered on top of an already demanding baseline effort. At these intensities, performance is constrained not by total energy availability but by the rate at which ATP can be generated and regenerated.
Higher carbohydrate availability increases glycolytic flux, supporting both immediate cytosolic ATP production and increased delivery of pyruvate to the mitochondria. This allows the entire energy system to operate at higher sustainable throughput, which helps explain why aggressive carbohydrate fueling improves performance even when muscle glycogen is not fully spared.
What Elite Athletes Actually Do
The review makes theoretical arguments about minimal carbohydrate needs. Although it should not be taken as objective scientific evidence, let me tell you what actually happens at the highest levels of the sport.
I work with athletes who have experimented with various fueling strategies, have access to the best sports science support available, have careers depending on marginal gains, and have zero interest in nutritional ideology. These athletes are systematically moving toward 90-120 g/h during racing. They're doing this because they feel better, recover better, and race faster when they do it.
The performance benefits are real and repeatable. Better pace maintenance late in races means the classic Ironman "death march" at mile 18 of the marathon becomes less severe or disappears entirely with adequate fueling. Faster time trial performance after prolonged work is exactly what the King and Smith studies showed, and it's what we see in training and racing.
Athletes also report that hard efforts feel more manageable when fueling is appropriate. This translates into better pacing, fewer late-race mistakes, and improved tactical execution. At the same external workload, perceived exertion is lower, a finding supported by applied field studies such as the mountain marathon research discussed earlier.
Perhaps the most overlooked benefit is recovery. Adequate carbohydrate intake during long and demanding sessions improves an athlete’s ability to absorb training. Athletes recover faster between hard days, tolerate higher training consistency, and maintain quality deeper into training blocks. Preserved cognitive function late in races further supports better pacing decisions and cleaner technical execution on both the bike and the run.
Reconciling the Science with Reality
The Noakes review makes important points about the limitations of the "fuel tank" model, the role of blood glucose in regulating performance, and the problems with blanket nutritional recommendations. Where it fails is in concluding that because preventing hypoglycemia is necessary, it must therefore be sufficient. However, preventing hypoglycemia is the floor for optimal fueling, not the ceiling.
The complete evidence from controlled trials, field studies, and elite practice shows that carbohydrate intake of 60-90 g/h consistently outperforms 10-30 g/h in performance tests. Many athletes benefit from intakes of 90-120 g/h, particularly in hard events longer than 3 hours. The mechanisms extend beyond glucose homeostasis to include sustained ATP flux, reduced physiological strain, and preserved neuromuscular function. Individual variability exists, but the general direction is clear. Higher than 10-30 g/h is better than lower.
The review's conclusion that 10 g/h (or ~15-30 g/h, which is states earlier in the review) is sufficient cannot be reconciled with either the controlled research or competitive reality.
What This Means For You
If you're trying to optimize your performance, don't limit yourself to 10-30 g/h based on this review. The evidence supports 60-90 g/h for most athletes pushing their limits in races longer than two hours, and perhaps more if you can tolerate it. Individual experimentation to find your optimal intake matters, and progressive gut training to increase tolerance is important.
The goal should be to build metabolic machinery that can handle high flux from both pathways, then fuel in a way that allows that system to operate near its capacity throughout competition. That's what adequate carbohydrate intake does. That's why elite athletes do it. That's what the review, for all its scholarly thoroughness, misses.
Start where you are. Build gradually. Don't let theoretical arguments about minimal needs prevent you from fueling adequately for maximal performance. The best athletes in the world consume 60-120 g/h+ during racing and hard training because it works.
Conrad Goeringer is an Ironman Certified Coach based out of Nashville, TN. He is the founder of Working Triathlete and author of the book The Working Triathlete. His passion is helping athletes of all levels and with all schedules achieve their endurance goals. Reach out to learn more about coaching packages and for a free consultation.